More simplifications of abi XML file

[Mark J. Wielaard]

Hi,

With the following patches I can reduce the output of the abi XML file
for libelf to under 100K.

 [PATCH 1/4] Add named-types-ids to use name ids after the type name
 [PATCH 2/4] Add no-parameter-names to drop function parameter names.
 [PATCH 3/4] Add --no-elf-needed option to drop DT_NEEDED list from
 [PATCH 4/4] Add --merge-translation-units option.

It is also simple to compare the XML output by hand with a simple diff
because it contains less (irrelevant) information and the output is
a little more stable.

The last issue for my use case are the anonymous structs, unions and
enums. I would like to find a way to use a more stable id for them.
This should be possible because they are normally embedded in something,
a larger structure or a typedef to name them which could be used to
give them a more recognizable id.

Cheers,

Mark